U.S. patent number 6,178,253 [Application Number 09/129,564] was granted by the patent office on 2001-01-23 for method of determining and treating the health of a crop.
This patent grant is currently assigned to Case Corporation. Invention is credited to Monte A. Dickson, Shufeng Han, Larry L. Hendrickson.
United States Patent |
6,178,253 |
Hendrickson , et
al. |
January 23, 2001 |
Method of determining and treating the health of a crop
Abstract
A process for determining the health of crops in a field and
treating the crops in accordance with that determination. The
process first establishes, in a field in which the health of the
crops is to be determined, at least one predetermined reference
area of crops having a determined nutrient, e.g. nitrogen, content.
Then, georeferenced aerial photographs are taken of at least a
portion of the field. From the photographs, the green plane is
determined. From the green plane, a relative greenness map of the
field based upon the nitrogen reference area is prepared. The
greenness map may be transmitted to a farm vehicle on the field and
thereafter, the field may be selectively treated in accordance with
the nutrient deficiencies detected and recorded on the greenness
map.
Inventors: |
Hendrickson; Larry L.
(Naperville, IL), Dickson; Monte A. (Naperville, IL),
Han; Shufeng (Darien, IL) |
Assignee: |
Case Corporation (Racine,
WI)
|
Family
ID: |
22440603 |
Appl.
No.: |
09/129,564 |
Filed: |
August 5, 1998 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
948637 |
Oct 10, 1997 |
|
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Current U.S.
Class: |
382/110; 348/144;
47/58.1R |
Current CPC
Class: |
G01J
3/2803 (20130101); G01J 3/2823 (20130101); G06K
9/00657 (20130101); G06K 9/2018 (20130101); G06T
7/0002 (20130101); G06T 7/0004 (20130101); G06T
7/40 (20130101); H04N 5/332 (20130101); G06T
7/90 (20170101); G06T 2207/10036 (20130101); G06T
2207/30188 (20130101) |
Current International
Class: |
G01J
3/28 (20060101); G06T 7/00 (20060101); G06T
7/40 (20060101); G06K 009/00 () |
Field of
Search: |
;382/110 ;702/2,5
;364/144 ;348/144,164 ;47/1.7,58.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Video Image Analysis as a Nondestructive Measure of Plan Vigor For
Precision Agriculture; Commun. Soil Sci. Plant Anal . . .
27(3&4), 607-614 (1996). .
Analysis of Aerial Photography For Nitrogen Stress Within Corn
Fields; Published in Agron. J. 88:729-733 (1996). .
Nitrogen Assessment in Wheat Using Computer Vision; Paper No.
962014; An ASAE Meeting Presentation Jul. 14-18, 1996. .
Sensor for on the Go Control of Site Specific Nitrogen Top
Dressing; Paper No. 961018; An ASAE Meeting Presentation; Jul.
14-18, Arizona. .
Remote Sensing of Plant Nitrogen Status in Corn; Presented in Part
as ASAE Paper No. 94-2117, .
International Search Report for PCT Application No. PCT/US98/21334.
.
Filella et al. "Evaluating Wheat Nitrogen Status With Canopy
Reflectance Indices and Discriminant Analysis", Crop Science, vol.
35, Sep.-Oct. 1995, pp.1400-1405. .
"Analysis of Aerial Photography for Nitrogen Stress Within Corn
Fields"; Blackmer et al.; Agron. J.; pp. 729-733 (1996). .
PCT Form/ISA/220; International Search Report for Application
PCT/US99/16426..
|
Primary Examiner: Au; Amelia
Assistant Examiner: Wu; Jingge
Attorney, Agent or Firm: Foley & Lardner
Parent Case Text
RELATIONSHIP TO OTHER APPLICATIONS
This application is a continuation-in-part of application Ser. No.
08/948637, filed on Oct. 10, 1997 and entitled "Method for
Monitoring Nitrogen Status Using a Multi-spectral Imaging System",
Case Docket No. 12,106.
Claims
What is claimed is:
1. A process for determining the health of crops in a field, said
field containing regions having differing areas of nutrient
containing crops, comprising the steps of:
establishing, in a field in which the health of the crops is to be
determined, at least one predetermined reference area of crops in
each of said regions to provide more region specific reference
values for said field, said reference areas having a determined
nutrient content;
georeferencing aerial photographs of multiple regions of said
field;
determining the green plane in the photographs thus taken; and
preparing a relative greenness map of the regions based upon said
nutrient reference areas;
wherein said nutrient reference areas include strips of nutrient
enriched crops to form nutrient enriched references, and said
regions are formed by subdividing said reference strips until each
region meets an established level of variability.
2. A process for determining the health of crops in a field in
accordance with claim 1, wherein the levels of variability are
based upon the variability of gray scale values within the
reference areas.
3. A process for determining the health of crops in a field in
accordance with claim 1, wherein said reference strips are
subdivided by halving until the variation in each region is less
than a predetermined value.
4. A process for determining the health of crops in a field, said
field containing regions having differing areas of nitrogen
containing crops, comprising the steps of:
establishing, in a field in which the health of the crops is to be
determined, at least one predetermined reference area of crops in
each of said regions to provide more region specific reference
values for said field, said reference areas having a determined
nitrogen content;
georeferencing aerial photographs of multiple regions of said
field;
determining the green plane in the photographs thus taken; and
preparing a relative greenness map of the regions based upon said
nitrogen reference area;
wherein said nutrient reference areas include strips of nutrient
enriched crops to form nutrient enriched references, and said
regions are formed by subdividing said reference strips until each
region meets an established level of variability.
5. A process for determining the health of crops in a field in
accordance with claim 4, wherein the levels of variability are
based upon the variability of gray scale values within the
reference areas.
6. A process for determining the health of crops in a field in
accordance with claim 4, wherein said reference strip is subdivided
by halving until the variation in each region is less than 10%.
7. A process for determining the health of crops in accordance with
claim 1, wherein the step of establishing a nutrient reference area
includes the step of applying a predetermined quantity of nutrient
to crops in said reference area.
8. A process for determining the health of crops in accordance with
claim 7, wherein said determining the green plane in said
photograph includes the step of differentiating soil and green
plants, in the photograph thus obtained.
9. A process for determining the health of crops in accordance with
claim 8, wherein the step of differentiating soil and green plants
includes the step of segmenting images to select crop pixels while
discarding soil pixels.
10. A process for determining the health of crops in accordance
with claim 9, wherein said segmenting images step includes the step
of separating the photographic image into green, red and near
infrared planes.
11. A process for determining the health of crops in accordance
with claim 1, wherein the step of determining the green plane in
said photographs includes differentiating soil and green plants by
segmenting images to select crop pixels while discarding soil
pixels.
12. A process for determining the health of crops in accordance
with claim 1, including the steps of taking aerial photographs of
the field and basing said relative greenness map upon greenness
values relative to said reference.
13. A process for determining the health of crops in accordance
with claim 12, wherein said aerial photographing step includes
taking a plurality of pictures in sequence, and piecing said
photographs together to form a composite of the field.
14. A process for determining the health of crops in accordance
with claim 12, including the step of:
establishing reference points in said field to facilitate global
positioning accuracy of photographed areas of the field.
15. A process for determining the health of crops in accordance
with claim 12, including the step of:
establishing reference points in said field to facilitate the
formation of a composite photographic representation of said
field.
16. A process for determining the health of crops in accordance
with claim 15, including the steps of:
applying nutrient to said field in accordance with said greenness
application map in georeferenced areas of nutrient deficiency.
17. A process for determining the health of crops in accordance
with claim 11, including the steps of segmenting red and near
infrared planes to determine the overall coverage of crop in the
field.
18. A process for treating crops in accordance with claim 1,
including the step of:
basing said relative greenness map based upon greenness values.
Description
FIELD OF THE INVENTION
The present invention relates to a method for determining the
health of crops in a field, and more particularly relates to a
method for determining the same by aerial photographic analysis
allowing for real time or near real time correction of deficiencies
in the health of the crop at any time during the growing
season.
BACKGROUND OF THE INVENTION
It is well known that monitoring of agricultural crops is desirable
to determine existing growing conditions so as to allow for
improvement and maximization of yields. While there is considerable
interest in remote sensing of crops in fields, most of the current
attention is directed towards identification of atypical areas of
fields that may indicate crop stress due to water, insect, disease
or weed pressures. Although some attention has been directed toward
identification of nutrient stress using remote sensing, the success
of such identifications is generally ineffective unless nutrient
stresses are sufficiently severe to reduce overall crop biomass.
Moreover, as the current focus in remote sensing is directed
towards anomaly detection, the most typical image product is a
false color image, or a three-spectral (wavelength) image combining
near infrared, red and green plane images with no better than
approximately one meter spatial resolution per pixel. While
interest is growing for better spatial resolution, the products
necessary for such are not currently available because of the
increase in cost and because file size increases exponentially with
resolution, the cost being disproportionate to any increase in
benefit obtained by an increase in information.
Other prior art regarding remote sensing for crop nitrogen
characterization has demonstrated that the intensity of red, green
and blue values of scanned color photographs is closely related to
corn yields on plots that had varying nitrogen fertilizer rates.
This relationship was determined during the late growing season,
well after the normal times of nitrogen fertilization. While the
results suggested that the different intensity values were due to
nitrogen rates this was not clearly demonstrated. Moreover, the
results did not demonstrate that the different intensity values
were related to crop nitrogen levels.
Researchers have demonstrated that nitrogen stress can be observed
using RGB aerial photos, but such observations have been
qualitative in nature, and have not yet been used as a basis for
immediate further nitrogen applications.
Still other prior art has demonstrated that hand-held chlorophyll
meters such as the "SPAD" sold by Minolta Corporation gives
measurements which are closely related to the nitrogen
concentration in individual plants, and that these readings from a
hand-held chlorophyll meter could be employed as a basis for
supplementing required nutrients such as nitrogen. Chlorophyll,
which is the related green pigments found in photosynthetic
organisms, has been found to be closely related to the amount of
nitrogen present in plants or crops. Thus, low chlorophyll
concentration levels have been found to be indicative of slower
growth in plants and ultimately lessening of yield in the crops in
the field.
One of the real discoveries that would allow for remote sensing and
analysis of the nitrogen contained in a plant in the field was the
ability to segment between soil and crop pixels so as to permit
discarding of the soil pixels and thus permit analysis only of the
green vegetation or crops. The advantage of this may readily be
seen because an analysis can start soon after the plants have
started their growth and are emerging from the soil. In other
words, a large mass of plant growth, which is usually exhibited
only very late in the growing season, is unnecessary and analysis
of the health of the crops may be obtained throughout the growing
season. This permits correction almost immediately upon discovery
of low nitrogen levels in the plants.
One way to analyze the health of the crop is to compare current
images with prior images to determine whether the nitrogen or
nutrient level is either the same, lower, or higher than in the
previous image. A major problem with that kind of analysis is that
the light present at different times of the day is difficult to
monitor effectively. Shadows that are cast upon the field or the
plants vary with light conditions, and in general lighting
conditions in which the photographs were being taken all affect the
green intensity. Therefore, comparison between previously taken
photographic images and/or data in recently taken photographs is
not conclusive as to whether or not the plants or crops are
healthy, or need additional nitrogen. Moreover prior aerial
photographic work was restricted to later in the growing season
because of the inability of distinguishing between soil and crop
pixels as well as mixed soil/crop pixels. Moreover, even when
restricting the aerial photography to late in the growing season,
shadows and the like, due to differences in lighting give
inconclusive results as to the health of the biomass or canopy
photographed. Additional discussions of prior art may be found in
the parent application of which this is a continuation in part, the
parent application being herein incorporated by reference.
Moreover, in many instances the time consumed in making a
determination of the health of the crop, where stress in the crops
due to lack of nitrogen poses a very real threat to yield. It is
essential that corrective action be taken as quickly as possible,
(i.e. within hours or days). Thus it is preferable in these
instances to immediately process, in real time, the aerial
photographs so that large amounts of data retention are unnecessary
and all that is required is to convey the resultant information on
the location of observed nitrogen deficiencies to the ground so
that nitrogen may be applied to the areas requiring treatment in
the field.
SUMMARY OF THE INVENTION
The present invention provides a process for determining not only
the health of crops in the field but the ability to take corrective
action as soon as realistically practicable. The process comprises
the steps of establishing, in a field in which the health of the
crops is to be determined, at least one predetermined reference
area having a determined crop nutrient or nitrogen content. Aerial
photographs of at least a portion of the field are obtained and
georeferenced to known ground positions. A relative greenness map
of the field based upon the nutrient or nitrogen referenced area is
then derived, the relative greenness map indicating places in the
field where the crops require immediate attention. The relative
greenness map may include a gray scale value applied in the
georeferenced file. The gray value map may be employed as the basis
for the nitrogen prescriptions, higher gray values indicating lower
crop nutrient or nitrogen concentrations which would require higher
levels of additional nutrients to reach maximum yields.
Concomitantly higher nutrient or nitrogen fertilizer rates would be
applied as the gray values increase.
The georeferenced "relative" greenness map provides crop status
information with spatial resolution equivalent to the spatial
resolution of the original aerial images. This "relative" greenness
map may then be converted directly to a nitrogen recommendation map
through the use of a look up table based upon the relative
greenness values and stage of crop development. For example, areas
of the field with relative greenness values similar to those of the
reference rows would receive little or no additional fertilizer,
while areas showing significant nutrient stress would receive much
higher rates. The actual rate recommended would also be based upon
stage of crop growth, with higher nitrogen levels required for
stress observed early in the season as compared to stress observed
closer to, for example, harvest. In crops such as small grains,
georeferenced maps of canopy extent can also be used to adjust
nitrogen recommendations. Other factors such as soil type,
available moisture, previous crop and manure applications would
also be considered to further adjust the recommended rates.
The process outlined above for determining the health of crops in a
field can be conducted at any time during the growing season by
segmenting or differentiating the soil and green plants in the
photographic images. Thus, in the early growing season, where soil
is predominately exposed in the photographic image, differentiating
or segmenting the soil pixels from the plant pixels will allow for
a more accurate determination of a comparison between the
"greenness" of the plants and the reference area having a
determined nutrient or nitrogen content. Moreover, by having a
predetermined reference area with a determined nitrogen content in
each frame of photographs, the effects of shadowing, different
times of day when the photographs are taken, etc. are diminished
because, the greenness of the crop within the frame is compared to
the reference strip in the frame.
The problems of resolution can be overcome by maintaining the
overflight photographs at a predetermined level from the ground,
the closer to the ground the better, with multiple frames being
shot in sequence and later the photographs being mosaiced or pieced
together to form a photographic image of the entire field. To this
end, it may be helpful to provide reference points throughout the
field or at least at close areas to the frame edges of the
particular height that the photographs will be taken which will
permit for easy piecing together of the frames thus taken to form a
picture of the entire field. Moreover, and even more importantly,
the reference points allow for greater accuracy of GPS position or
registration of the aerial photograph to the ground GPS
position.
It should be recognized that nitrogen stress (i.e. deficiency of
nitrogen) in a crop causes symptoms that are almost identical to
those caused by a lack of sulphur. Thus the finding of nutrient
stress in the plant by the technique and process of the present
invention, may be employed, along with knowledge of the field in
which the crop is placed, to correct deficiencies other than just
nitrogen. For example, an appearance of lack of greenness may be,
after a study of the affected area, a determination that an
insecticide or fungicide might be needed as well as nitrogen, or
that a deficiency in greenness is caused by a lack of moisture, or
insufficient sulphur. While principally the stress will be due to
insufficient nitrogen, it should be recognized that other nutrient
deficiencies may be found by the process of the present inventions.
Moreover, upon recognition of other nutrient deficiencies, sulphur,
iron or other nutrients may be applied to correct the
deficiencies.
Other advantages of the invention and a more complete understanding
of it may be obtained with reference to the following specification
and claims taken in conjunction with the accompanying drawings in
which:
DRAWING DESCRIPTION
FIG. 1 is a view in plan of a portion of a field to which the
process of the present invention is to be applied;
FIG. 2 is a view similar to FIG. 1 but in which a predetermined
area, in the illustrated instance two rows, has been treated with
an excess of nitrogen fertilizer to provide reference rows, strips
or areas to facilitate the determination of the health of the crops
in the field and in accordance with the process of the present
invention;
FIG. 3 is a flow chart illustration of the process in accordance
with the present invention;
FIG. 4A is an enlarged view in plan of a portion of the field
illustrated in FIG. 4B, illustrating an added feature of the
present invention, in which each portion of the field to be
photographed, may contain reference points to facilitate greater
accuracy of GPS registration between the aerial photograph and the
field;
FIG. 4B is a fragmentary schematic view in plan of such a composite
field photograph;
FIG. 4C is a side elevational view of a plane with a camera
attached and photographing sequentially predetermined areas
corresponding to the areas schematically illustrated in FIGS. 4A
and 4B;
FIG. 5 is a view of a self propelled sprayer or applicator having
mounted thereon fertilizer tanks or bins for application of
nutrients, e.g. nitrogen at predetermined selected locations in
accordance with the invention and where determined that there is a
nutrient deficiency; and,
FIG. 6 is another flow chart in which the images from the digital
camera may be segmented to not only display the percentage of
canopy of the crop, but also to allow the conversion of the green
images to a gray value image to facilitate easy identification of
nutrient deficiencies, and their locations. This Figure also
describes the method for relating greenness maps and canopy maps to
provide nitrogen application maps.
DESCRIPTION
Referring now to the drawings, and especially FIG. 1 thereof, a
portion of a field 10 having a plurality of plant containing rows
11, 12, 13, 14, 15 and 16 are illustrated therein. Between the
individual rows, and surrounding the individual plants in a row is
soil or earth. In accordance with the invention, and referring now
to FIG. 2, in each of the fields for which the health of the crops
is to be determined, at least one predetermined reference area of
the crops having a determined nutrient, in the present instance
nitrogen, content is provided. In the illustrated instance, rows 12
and 13 have been provided with extra nitrogen fertilizer, slightly
more than the general amount that would normally be applied to the
remainder of the field during planting. For example, if 100 pounds
of nitrogen is to be applied per acre to a particular field, rows
12 and 13 are provided with fertilizer at a rate of 110 to 120
pounds per acre. It should be understood that these high nitrogen
reference strips may be typically wider than a single row. The
single rows designated are for illustration only.
It should be understood that the high nitrogen reference strips,
such as rows 12 and 13, may be subdivided to provide reference
areas with appropriate gray level values. The reason for utilizing
an excess of nitrogen to establish the reference strips is to
insure that nitrogen is not limiting the growth or reflectance of
plants growing in the strips. It should be recognized that both
growth and reflectance are also impacted by other field
characteristics, such as the level of other nutrients, e.g.
moisture, sulphur or even other environmental or soil condition
factors. Thus if an average gray level for the entire strip or row
was utilized, an inappropriate reference value for a particular
portion of the field may be employed. This could cause over or
under application of nitrogen to some adjacent regions of the
field.
To circumvent this problem, it may be desirable to subdivide each
reference strip to provide a more region specific reference value
for all areas of the field. The number of subdivisions will, of
course, depend upon the variability of the field. Historical
references to particular fields may be employed to determine the
variability of particular fields. If a field is relatively uniform,
a single value for each reference strip is appropriate.
Alternatively, more subdivisions may be necessary in regions of the
field that are more variable (based upon the variability of gray
scale values within the reference rows.)
One approach employed for subdivision is to repetitively halve each
reference strip until each new subdivision meets an established
level of variability. For example, the halving process may be
continued until the coefficient of variation is less than a
selected value, e.g. 10%. Of course other procedures for
establishing appropriate gray level values to use as reference
value may be employed to provide more region specific reference
values for all areas of the field.
The application of the fertilizer may be conventionally done and is
schematically illustrated in FIG. 5 as by a farm vehicle, in the
illustrated instance, a self propelled sprayer 100 containing
fertilizer bin 140 mounted thereon. The self propelled sprayer 100
includes an operator controlled cab 120 thereon. The sprayer 100
contains conventional engine and drive train which are coupled to
driven front and rear wheels 122 and 124 respectively. As shown,
the sprayer 100 includes a frame 142 upon which is mounted thereon
the bins 140 for applying nitrogen rich fertilizer as through a
delivery system 152 to selected plants in predetermined rows in the
field 10. The sprayer 100 may also include herbicide/insecticide
containers and applicators (not shown). Alternatively, the bin 140
may contain other nutrient feed bins either for liquid or granular
dispensing. Note: early in the growing season or with crops that do
not grow to great heights, a tractor with towed implement
containing fertilizer applicators may be employed.
The cab 120 of the farm vehicle includes a cab display unit 125
which may be connected to a data processing unit such as a computer
and the like, as well as to a global positioning system (GPS)
signal receiver and an associated differential DGPS signal
receiver. The GPS and DGPS receiver may be manufactured for example
by Trimble Navigation Ltd. of California, while the (differential
signal) may be provided by Omnistar, Inc. of Arizona. The receiver
determines the longitude and latitude coordinates of the farm
vehicle from signals transmitted by the GPS satellite network. The
accuracy of the location data is improved by applying correction
signals received by the DGPS portion of the receiver. The
differential correction signals are employed to correct errors
present on the GPS signals including the selective availability
error signal added to the GPS signals by the U.S. Government. As
will become more evident hereinafter, a fertilizer correction
signal for georeferenced portions of the field may be applied or
transmitted to the farm vehicle, or to a base station, as from an
aircraft or the like that has analyzed the health of the field, as
by the method of the present invention.
Turning now to FIGS. 3 and 4C, the first step in the process of the
present invention (subsequent to establishing at least one
predetermined reference area of crops having a determined nutrient
(e.g. nitrogen) content) is to obtain photographic images of at
least portions of the field while georeferencing the areas on the
photographs. To this end, an airplane or aircraft 20 is illustrated
in FIG. 4C with a camera 26 depending therefrom to take photographs
of at least portions of the field 10. The resolution of a camera
designed to take such photographs may include the design set forth
in the parent application. Alternatively, a digital color camera
such as a Kodak DCS 460 may be employed. Assuming an aircraft
height over the earth of approximately 1,000 feet, a single frame
may result in a picture of approximately 25 acres. Since the Kodak
camera has approximately 3,000 by 2,000 pixels (6,000,000 pixels)
in one frame, assuming a 25 acre per frame photographic image or
data, and inasmuch as one acre equals 43,560 square feet, each
pixel covers 0.1815 square feet or an area of 5.112 inches by 5.112
inches. While the Kodak camera has a single CCD with a striped
filter masked on the CCD, the color camera described in the parent
application includes 3 CCD arrays which individually detect the
same scene in three different wave length ranges: green, red, and
near infrared. As discussed in the parent application, the optional
wavelengths for crop characterization are green in the wavelength
range of 550 nm(+/-20 nm), red in the wavelength range of 650 nm
(+/-40 nm) and near infrared in the wavelength range of 800 nm
(=/-40 nm). Of course, different bandwidths may be used.
Additionally, the specific optimized wavelengths may depend on the
type of vegetation being sensed. Thus in the above example, the
area of each pixel in the field of view is approximately 26.136
square inches when the field of view is 25 acres. When the aircraft
is closer to the ground, the frame will cover fewer acres and
therefore the area of each pixel in the field of view will be
considerably less.
After a photograph of a portion of the field is taken by the camera
26 mounted in the plane 20, and as depicted in box 30 of FIG. 3,
the photograph is analyzed as at 40 in FIG. 3. The CCD arrays in
the camera, and as is conventional in cameras of this type,
convert, by an A/D converter, the signals for green, red and near
infrared into digital signals and the data from these signals may
be employed for analysis of crop characteristics of the imaged
vegetation, (i.e. the vegetation or plants or crops in the field
10).
In this connection the green intensity in reference rows 12 and 13
may be compared to the green intensity for the remaining portion of
the frame, such as indicated at box 50 and if the entire frame's
green intensity is equal to the reference intensity, clearly no
further nitrogen must be applied to the field. Whatever the
comparison may be, as illustrated in block 60, the green intensity
is referenced to the reference intensity and this relative
greenness value can be related to its position in the field to form
a map which can be referred to as a "relative greenness" map,
hereinafter referred to as a "greenness" map 70. By handling the
greenness intensity with reference to the reference intensity in
this manner, a simple ratio can be placed on the greenness map
illustrating the percentage of greenness of any particular portion
of the frame relative to the referenced intensity which will
indicate whether further nitrogen is required. Inasmuch as the plot
is georeferenced, the location on the field of that particular
frame is assured. The aircraft then may proceed in sequence to the
next adjacent plot or portion of the field (with some overlap) and
take another photograph. In passing it is noted that this is much
like a step-and-repeat operation.
In the event that the photographs have been taken early in the
growing season, where plant size is relatively small as compared to
the exposed soil in the field, by employing only the green plane
and comparing its contents to the reference green intensity, and
ignoring or segmenting the soil pixels, the health of the field at
any portion of the growing season may be determined. Moreover,
because of the ability to georeference the information taken from
the camera, locations where additional nitrogen is required to
enhance the yield of the field is readily viewable and available to
the operator. As set forth heretofore, there are three principal
and useful wavelengths, and images are formed in the camera for
light reflected at each of the wavelengths. A red image, a near
infrared image and a green image are formed from the CCD arrays
with the camera.
Crop pixels tend to absorb red and reflect infrared wavelengths.
This determines whether a particular pixel is crop or soil. If
soil, this pixel may be discarded, and the health of the crop is
determined by light reflectance in the green plane for the
remaining pixels.
Additionally, by segregating the soil pixels and comparing the
percentage of the image pixels remaining after separating the soil
pixels, (see blocks 42 and 44 in FIG. 3), the percentage of
coverage of the portion of the field by vegetation may be
determined. This is commonly referred to as canopy coverage.
As the plane takes photographs that are step and repeat along the
field in, for example, approximate 25 acre frames, it is essential
that the GPS positions within this image are accurately locatable
so that application of nitrogen based upon GPS position is applied
to the correct areas.
In this connection, it is desirable that the frames may be pieced
together to form a composite of the field. The composite is much
like piecing together a crossword puzzle or a mosaic and the manner
in which accurate GPS position is assured may also be employed to
establish reference points in the field which appear in each frame
when the photograph is being taken.
Moreover, and more importantly the reference points allow for
greater accuracy of GPS position or registration of the aerial
photograph to the ground GPS position. To this end, and referring
now to FIGS. 4A and 4B, referenced areas may be placed at the
corners of each map frame, such as shown at 65, 66, 67 and 68 of
each 25 acre frame or plat 10a. The reference points in the field
may be located in any convenient manner, and may even incorporate
high nitrogen areas or be incorporated as part of the rows in which
high nitrogen has been incorporated. Moreover, inasmuch as shadows,
lighting and so forth play such an important part in determining
the intensity of the reference with regard to the intensity of the
greenness of the leaves of the crop, it is preferable that at least
one such high intensity reference (i.e. reference nitrogen level)
be incorporated in each frame. Thus the references 65-68 may serve
the important function of insuring greater accuracy of GPS
registration of air/ground GPS position, but also facilitates the
placing of, for example, frame 10a in position with regard to
frames 10b, 10c, 10d through 10i. It should be recognized that the
reference areas may be bare or plantless areas, different color
dyed areas, and may be located in any convenient pattern. For
example, the frame reference point may be a bare area in the middle
of each frame.
Thus the greenness map 70 may be composed by computers on the
aircraft in real time, thus saving in storage requirements. Of
course the map may be transmitted to the farm vehicle 100 in the
field and nitrogen deficiency correction may start almost
immediately, if desired. Inasmuch as nitrogen deficiencies are
georeferenced, and the sprayer operator, through his on board
global positioning system knows exactly where he is, immediate or
later application of nitrogen is relatively easy.
Referring now to FIG. 6, the segmented images such as shown at 40
in FIG. 3 may be separated so as to give a green only image at 75
from which the percentage canopy image may be calculated or derived
as at block 76 to generate a Geographic Information System (GIS)
type map. Moreover, the green plane image, such as shown in blocks
78, may be utilized by a GIS Program to provide a gray scale value
for exact positions within the field as at 79. The gray scale image
may then be converted to a grid and or contour GIS map which may be
applied as at 81 relative to the reference strips and to the grid
and contour GIS map as at 82 (for defining even, subdivided areas
of the reference strips). The resultant "relative" greenness maps
and or the percentage canopy maps may then be used to develop the
prescriptions necessary to form a nitrogen application map 83 which
maps the application areas and/or rates necessary to bring the crop
in the field up to some desired level of nitrogen. For example,
application map 83 may indicate the nitrogen fertilizer required to
ensure sufficient levels for the remainder of the growing
season.
It should be recognized that later in the growing season where the
crop canopy reaches almost 100%, there may be little reason to
differentiate between soil and green plants because the entire
field is vegetation. The only difference in the field will be areas
that require more nitrogen fertilizer to bring the greenness level
back to that which it should be for proper and maximum plant or
crop yield.
As described in the parent application, crop nitrogen status may
also be identified or described using ratios of various image
planes, such as green/near infra red or red/near infrared. Thus, a
normalized difference vegetative index (NDVI) or green NDVI may be
employed to separate the vegetation pixels from the non-vegetation
pixels and therefore may be employed in lieu of green plane
determination to determine N status. For example, as taught in the
parent application, the NDVI index for each pixel may be calculated
by subtracting the red value from the near infrared value and
dividing the result from the addition of the red value and the near
infrared value. The vegetation image map is generated using the
NDVI value for each pixel in the multi-spectral image. In these
instances, it may also be advantageous to provide high nitrogen
reference strips. Vegetation indices, like NDVI, will likely be
more useful during the earlier growing season in situations where
segmenting out soil is difficult because of insufficient spatial
resolution. Because vegetation indices include information about
relative soil coverage and also about crop chlorophyll levels, such
vegetation indices may be used along with or as an alternative to
relative greenness maps.
This could be accomplished in much the same manner as has
heretofore been described except would utilize a developed layer
(NDVI) instead of just the green plane. In this instance, the
nitrogen status would be evaluated by the ratio of NDVI values for
each pixel with the NDVI value for the adjacent high nitrogen
reference strip.
As described, the georeferenced "relative" greenness map provides
crop status information with resolution equal to the spatial
resolution of the original aerial images. The map may then be
converted to a nutrient (e.g. nitrogen) recommendation map via a
look up table based upon the relative greenness values and stage of
crop development. In this manner areas of the field showing
significant nutrient stress would receive a necessary dose of
nitrogen while areas with relative greenness values similar to
those of the reference rows would receive little or no additional
fertilizer. Of course the recommended rates of fertilizer
application would depend upon several factors such as stage of crop
growth, (higher levels of nitrogen being required for stress
observed in early growing season as compared to more mature crop
stress closer to harvest.)
While the embodiments illustrated in the various drawings described
above are presently preferred, it should be understood that those
embodiments are offered by way of example only. The invention is
not intended to be limited to any particular embodiment but is
intended to extend to various modifications that nevertheless fall
within the scope of the appended claims.
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